diff --git a/apps/site/src/components/pdpp-concept/concept-page.tsx b/apps/site/src/components/pdpp-concept/concept-page.tsx
index 2474c1b68..c56dc04da 100644
--- a/apps/site/src/components/pdpp-concept/concept-page.tsx
+++ b/apps/site/src/components/pdpp-concept/concept-page.tsx
@@ -31,7 +31,8 @@ export function PdppConceptPage({ children, home = false, className }: ConceptPa
         "lg:has-[>[data-slot=pdpp-concept-rail]]:grid-cols-[var(--spacing-rail)_minmax(0,1fr)]",
         "lg:has-[>[data-slot=pdpp-concept-rail]]:gap-x-gutter",
         // Short pages (home / 404): trim doc bottom pad
-        home && "**:data-[slot=pdpp-concept-doc]:pt-7! **:data-[slot=pdpp-concept-doc]:pb-5!",
+        home &&
+          "**:data-[slot=pdpp-concept-doc]:pt-7! **:data-[slot=pdpp-concept-doc]:pb-5! max-md:**:data-[slot=pdpp-concept-doc]:pt-0!",
         className
       )}
       data-slot="pdpp-concept-page"
@@ -52,7 +53,7 @@ export function PdppConceptDoc({ children, className }: ConceptDocProps) {
         // components.css — not on this shell (tables/terminal stay wide).
         "min-w-0 max-w-full pt-[calc(var(--spacing-section-gap)/1.5)] pb-[calc(var(--spacing-section-gap)*1.25)]",
         // max-lg
-        "max-lg:pt-[calc(var(--spacing-section-gap)/3)] max-lg:pb-[calc(var(--spacing-section-gap)*0.75)]",
+        "max-md:pt-0 max-lg:pt-[calc(var(--spacing-section-gap)/3)] max-lg:pb-[calc(var(--spacing-section-gap)*0.75)]",
         "[&_[data-slot=pdpp-concept-text]_a]:link-prose",
         "[&_a:not([class])]:link-prose",
         className
diff --git a/apps/site/src/styles/surfaces/specification.css b/apps/site/src/styles/surfaces/specification.css
index b5122825e..b4ceb0d05 100644
--- a/apps/site/src/styles/surfaces/specification.css
+++ b/apps/site/src/styles/surfaces/specification.css
@@ -90,14 +90,16 @@
   [data-pdpp-doc-theme] #nd-docs-layout {
     --fd-banner-height: 4rem;
     --fd-docs-height: calc(100dvh - 4rem);
+    /* Fumadocs reserves 3.5rem here by default, but the concept subnav is
+       3rem. Keep the grid row equal to the rendered header. */
+    --fd-header-height: 3rem;
     /* The table scrollport outsets through the article's right inset. The grid
        otherwise clips that extra width before it reaches the outer container. */
     overflow-x: visible;
   }
 
-  /* Keep one sticky navigation affordance: the sidebar trigger. The separate
-     TOC popover duplicates that navigation and is the row that crosses the
-     article while scrolling. */
+  /* Keep the sticky navigation row opaque while the TOC popover remains
+     available from its trigger. */
   [data-pdpp-doc-theme] #nd-subnav {
     background: var(--pdpp-concept-paper) !important;
     /* Paint over the table's right-hand bleed without extending the subnav
@@ -106,10 +108,6 @@
     backdrop-filter: none;
   }
 
-  [data-pdpp-doc-theme] [data-toc-popover] {
-    display: none;
-  }
-
   [data-pdpp-doc-theme] #nd-page.pdpp-docs-page {
     padding-inline: 0 !important;
   }